The present invention relates to a method for the serial application of labels on a tape.
Such a tape may, for example, be a packaging film, on which consecutive rows of labels are deposited. The film with the labels may subsequently be used for sealing packages.
For applying the labels, the tape initially is passed along an applicator, which deposits the labels serially on the tape. After or already during the deposition of a row, the tape is shifted by a length section, in order to make available a free section of tape for depositing a subsequent row. This step of advancing the tape by a length section after or during the deposition of a row of labels will be referred to in the following as a partial advance.
For the previously customary labelers, this partial advance takes place in that a pull loop downstream from the applicator is pulled by means of a tension roller out of the traveling path of the tape, while the section of the tape upstream from the pull loop is kept stationary. This means that the partial advance at the applicator takes place with the tape drive at rest, while the tension roller moves independently of the tape drive.
In a conventional mode of operation, initially a set of label rows is completed with the tape driving mechanism at rest in that the applicator deposits several rows one behind the other on the tape, which is moved further here in several partial advances. Subsequently, with the help of the tape driving mechanism, a section of the film, comprising a corresponding set of labels, is deposited on the packages. For example, the advance of the package lanes can be used as a tape driving mechanism, through the pulling action of which the tape is moved a segment of its length further.
For conventional labelers, the tension roller for forming the pull loop is moved pneumatically between two stops, which limit the travel of the tension roller. For example, while the tape driving mechanism is stationary, such a tension roller is pulled pneumatically against an upper stop and can later on fall back once again into its initial position. This type of loop formation has several disadvantages. At high operating speeds, the labels are not always positioned with sufficient accuracy, since the stops of the tension roller cannot always be set with a sufficient accuracy. The reproducibility of the positioning of the labels also suffers from this. The quietness of the running of the labeler is affected adversely and the overall height is increased. Finally, the running times of the pneumatic cylinder may fluctuate, for example, due to the effect of temperature and of pressure fluctuations in the system.
The preparation of a set with a large number of rows of labels is a particular problem, since a partial advance must be brought about for each row with the help of a separate loop. This means that there must be a tension roller for each row. For a large number of rows per set, the construction expense is hardly justifiable anymore and a change in the mode of operation of the machine leads to an appreciable expense for retrofitting. In particular, this system is relatively inflexible, expensive and error prone.